Area-Scalable Zn₂SnO₄ Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Modules

The development of a scalable chemical bath deposition (CBD) process facilitates the realization of electron-transporting layers (ETLs) for large-area perovskite solar modules (PSMs). Herein, a method to prepare a uniform and scalable thick Zn₂SnO₄ ETL by CBD, which yielded high-performance PSMs, is reported. This Zn₂SnO₄ ETL exhibits excellent electrical properties and enhanced optical transmittance in the visible region. Moreover, the Zn₂SnO₄ ETL influences the perovskite layer formation, yielding enhanced crystallinity, increased grain size, and a smoother surface, thus facilitating electron extraction and collection from the perovskite to the ETL. Zn₂SnO₄ thereby yields PSMs with a remarkable photovoltaic performance, low hysteresis index, and high device reproducibility. The champion PSM exhibited a power conversion efficiency (PCE) of 22.59%, being among the highest values published so far. In addition, the CBD Zn₂SnO₄-based PSMs exhibit high stability, retaining more than 88% of initial efficiency over 1000 h under continuous illumination. This demonstrates that CBD Zn₂SnO₄ is an appropriate ETL for high-efficiency PSMs and a viable new process for their industrialization.